%I A050721
%S A050721 2,3,11,109,173,5513600773
%N A050721 Primes arising in A083571.
%C A050721 Prime indices of palindromic triangular numbers.
%H A050721 P. De Geest, <a href="http://www.worldofnumbers.com/subtria.htm">Subsets 
               of palindromic triangulars</a>
%Y A050721 Cf. A008510, A050722.
%Y A050721 Sequence in context: A065378 A161721 A079853 this_sequence A058114 A042337 
               A061482
%Y A050721 Adjacent sequences: A050718 A050719 A050720 this_sequence A050722 A050723 
               A050724
%K A050721 nonn,base,hard
%O A050721 1,1
%A A050721 Patrick De Geest (pdg(AT)worldofnumbers.com), Sep 15 1999.